Simple amber lights could make nights safer for insects

The Alarming Decline in Nocturnal Biodiversity

Globally, approximately 40% of insect species are currently considered to be in decline and threatened with extinction. Among the main factors contributing to this phenomenon are the loss of natural habitat, pollution, and climate change. Artificial lighting from streetlights and security lights also poses a major threat to these populations.

Artificial light sources pose a significant problem for nocturnal insects such as moths, flies, and beetles. Attracted by the light, many of them eventually die of exhaustion after circling for hours. Furthermore, these lights disorient flying insects and divert them from vital activities such as foraging, reproduction, or their natural movements.

A recent study conducted by a team at the Leibniz Institute for the Analysis of Biodiversity Change in Germany and published in the journal Biological Conservation by Carmen Ludreschl and her colleagues demonstrates that a simple modification to outdoor lighting systems could reduce the impact of this threat.

A full-scale experiment in Germany

Scientists already knew that certain wavelengths of light are less attractive to insects. To explore this further, the researchers tested three types of outdoor lighting to determine precisely which ones attract the fewest insects.

The experiment took place at six rural train stations located in the heart of a German Dark Sky Reserve, a protected area where artificial light is minimized to preserve natural darkness. The trials spanned the field seasons of 2023 and 2024.

During this research, various commercial lighting options were compared with one another and against unlit control sites. To measure the actual impact of the installations, the team used traps to track the number of insects captured, their total biomass, and the diversity of species observed.

Amber LEDs Show Remarkable Effectiveness

The study’s findings show an indisputable result. According to the scientists involved in the study, “Commercially available 1800 K amber LEDs consistently attracted fewer individuals and species than high-pressure sodium lamps and 4000 K LEDs under in situ conditions throughout the study period.”

Compared to high-pressure sodium (HPS) lamps and cool-white 4,000 K LEDs, the warm amber 1,800 K lights reduced the total number of insects captured by approximately 39% to 51%.

Equally significant, the total biomass of trapped insects decreased by 51% to 77% under these amber bulbs, confirming the drastic reduction in insect activity around lighting fixtures using this color temperature.

Challenging Common Misconceptions About Warm Light

The study also revealed an unexpected finding: high-pressure sodium vapor lamps proved to be just as attractive to insects as cool-white 4000 K LEDs.

This finding directly challenges the popular belief that any light with a warm appearance is automatically safer for nocturnal biodiversity. The key distinction lies specifically in the spectrum emitted by 1,800 K amber LEDs.

Precise differentiation based on wavelength is therefore essential for designing street lighting systems that are truly suited to the conservation of nocturnal wildlife species.

Necessary Compromises for Species Conservation

Although 1,800 K LEDs represent a significant improvement, the researchers note in their report that any light source still has a negative impact compared to the complete absence of light. As stated in the article published in Biological Conservation, “Although the 1,800 K LED was the least attractive light source in our study, it still attracted more individual arthropods and a greater total number of species than the unlit control.”

This solution nevertheless represents concrete progress. Following the conclusions of this research, the platform lighting at all six train stations studied within the Dark Sky Reserve has been fully converted to 1,800 K amber LEDs.

This equipment upgrade provides a pragmatic solution for balancing the safety of human facilities with the reduction of disturbances to insect populations.

Source: phys.org

Simple amber lights could make nights safer for insects